Play Diagonal lines puzzle (Slant) online Works — plays right here, unlimited puzzles
Guide updated October 2026 · Runs via WebAssembly (native port)
Slant is a grid logic puzzle. Every square gets one diagonal line, either \ or /, and the numbers on the grid corners tell you how many lines must touch that point. The lines must never close into a loop. Each puzzle has one solution that you can reach by deduction. The puzzle is ready below; the default grid is small, and larger sizes are on the Type menu.
Controls — what does what
| Action | Keyboard | Mouse / touch |
|---|---|---|
| Place \ (top-left to bottom-right) | Enter, or the \ key | Left-click a square |
| Place / (top-right to bottom-left) | Space, or the / key | Right-click a square |
| Cycle blank, \, / in a square | Press Enter or Space again | Keep clicking the same button |
| Clear a square | Backspace | Click until it is blank |
| Move the cursor | Arrow keys | - |
| Undo / redo | U or Ctrl+Z / R or Ctrl+R | Game menu |
FREE This is the complete game, free. Open source under the MIT licence: the complete puzzle, with a new grid every time.
Slant is from Simon Tatham's Portable Puzzle Collection, © Simon Tatham and contributors, used under the MIT licence. Built from source by scripts/build-puzzles.mjs.
How to play
- Put exactly one diagonal line in every square, slanting one way or the other.
- A circled number on a grid point means exactly that many lines end at that point: 4 makes a cross, 0 means no line touches it.
- The lines must never form a closed loop anywhere on the grid.
A 0 can only appear on the edge of the grid, because a 0 in the middle would force a small diamond around it, which is a loop.
Sizes and difficulty
The Type menu offers 5x5, 8x8 and 12x10 grids, each at Easy or Hard. Easy puzzles can always be solved one square at a time. Hard puzzles need you to reason about relationships between squares, for example knowing two squares slant the same way before you know which way, but they never need guessing. Custom lets you set any width, height and difficulty.
Solving tips
Start with the edges: a 0 on the border fixes the squares beside it, and a 1 in a corner of the grid fixes that corner square. A 2 on the border fixes both squares beside it, and a 4 fixes all four squares around it. Then watch for loops: if one line would close a ring, the square must slant the other way.
Where this puzzle comes from
Slant is part of Simon Tatham's Portable Puzzle Collection, a set of about forty logic puzzles written by Simon Tatham and contributors and released under the MIT licence. Every grid is generated on the spot, so the supply never runs out, and for the grid-logic puzzles the generator makes sure each has exactly one solution, reachable by reasoning rather than guessing. The version here is the collection's own code compiled to WebAssembly; the Game menu can save a puzzle to a file and load it again, and the Type menu changes the size and difficulty.
Frequently asked questions
Why can't I use guesswork in Slant?
You can, but you never have to. Every generated puzzle, even at Hard, can be finished by logic alone, so if you are stuck there is a deduction you have not spotted yet.
Who invented Slant?
It is a Nikoli puzzle, published in Japan as Gokigen Naname. This version is the one in Simon Tatham's Portable Puzzle Collection, which generates a new grid every time.
Is Slant free to play here?
Yes, with no limit on the number of puzzles. Slant is open-source software under the MIT licence, and every grid is generated fresh when you press New game.
Does it work on a phone or tablet?
Yes. A tap works as a click and the puzzle resizes to fit the screen. Puzzles whose controls use the right mouse button are easier with a mouse.
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